As its name suggests, Muhyozawa (rime valley) is a place where you can have a good view of rime. Rime is made when super-cooled mist or clouds are blown onto tree branches or other objects by the wind and get frozen instantly on impact. It therefore grows upwind like a blade.
Myhyozawa is an ideal place to observe the rime, since its altitude is over 1,300 meters, its temperature is low due to the lack of sunlight blocked by the rocky hills on the south, and the north-west wind gathers along its east-west valley in winter.